With app slicing, developers can mark off the sections of an app that are specific to, say, an iPad. Then, when a 16GB iPhone owner who is worried about free space enables app slicing, the device won't download the iPad-specific sections. It can even be narrowed down to specific devices, so you don't download things for iPhone 5s if you have an iPhone 6, for example.

Unfortunately, you'll have to wait if you're running out of space. "App slicing is currently unavailable for iOS 9 apps due to an issue affecting iCloud backups created from iOS 9 where some apps from the App Store would only restore to the same model of iOS device," Apple said on its developer site.

"When a customer downloads your iOS 9 app, they will get the Universal version of your app, rather than the variant specific for their device type," Apple said. "TestFlight will continue to deliver variants for your internal testers. App slicing will be reenabled with a future software update. No action is needed by you at this time."

Apple is not indicating when app slicing might launch. Hopefully it'll arrive soon, for those of you still purchasing Apple's measly 16GB iPhones or iPads. Live Photos are going to eat up a chunk of your storage, after all.